The Machine Empire was a massive alien race and galactic empire of mechanical beings, led by the Royal House of Gadgetry. Possessing countless Cogs, Quadra Fighters, and monsters, the Machine Empire had already conquered an entire chain of galaxies before reaching Earth. It was when the Empire arrived on Earth that they finally encountered a foe capable of repelling their forces, the Zeo Rangers. Numerous monsters from the Empire perished at the Rangers' hands before King Mondo himself took to the battlefield and was destroyed by the Super Zeo Megazord.

It was during Mondo's absence that the Empire was led by , a renegade robot created by Lord Zedd and Rita Repulsa. Louie meant well, but squandered the Empire's forces, and was eventually overthrown by Mondo and Machina's eldest son, , and his wife, . The two led the Machine Empire against the Zeo Rangers rather well, initiating a massive, all-out invasion on Angel Grove. After this invasion failed, King Mondo returned, causing Gasket and Archerina to flee. When the Royal House of Gadgetry were later destroyed by Rita and Zedd, the Machine Empire went into a period of inactivity, useless without the Royal House to lead it.

The Royal House of Gadgetry was later rebuilt by forces unknown, and the Machine Empire joined the United Alliance of Evil under the command of Dark Specter, the Grand Monarch of Evil. When Dark Specter initiated his universal invasion, the Machine Empire invaded KO-35 and the Phantom Ranger's homeworld, conquering both planets and defeating the Karovan rebels, the Phantom Ranger, and the Blue Senturion. When Zordon's energy wave struck these planets (during Countdown to Destruction), much of the Machine Empire (including King Mondo) was destroyed, every member of it reduced to a pile of sand.